The problem of designing an interface between the continuous-state and the discrete-state domains of intelligent control architectures is addressed, focusing on the case of a hierarchical navigation, guidance and control (NGC) architecture for unmanned underwater vehicles. The proposed interface represents the underlying continuous-state execution level as a discrete event system using a Petri net formalism. The correct behavior of the execution level is ensured, checking that no forbidden state is reached and that the proper task activation and deactivation order is respected. Methodologies for the off-line generation of the Petri net representation of the execution level and automatic system reconfiguration are presented.